Passive Solar for an energy efficient dwelling
Posted on Sep 24, 2008 - 04:22 PM
By: Jayanth Krishnappa
Your home or office is subjected to various climatic conditions, be it local, regional and more generally global. All variations influence the design of your building in relation to the sun. Poor design of buildings in terms of utilizing solar energy causes buildings to overheat and cause discomfort. This is recognized in most building with ‘modern’ architecture where looks of the design have become the priority over their functionality. As a result, your cooling and heating bills gain weight. They say that the sun can be your friend or enemy in buildings. Therefore, the free energy of sun should be utilized in buildings in such a way that it does not interfere with the comfort and economy of the occupants.
Passive solar is a phenomenon in which the solar radiation is transmitted through a protective glazing layer(s) on the facade of the building into its inner space and is absorbed and stored by thermal mass like masonry walls, floors and other entities.
The most common passive solar energy device in building is the window. The glass pane allows light and heat in the form of short wave radiations to enter the building space. During this process, some of the energy is absorbed and some reflected back. The internal surfaces of the building re-emit long wave radiations, which are not allowed to pass through the window glass and hence, the energy is trapped and later expended for heating the inner space of the building.
- The main processes involved are:
- Absorption – to collect solar energy, windows on the south facing side of the building are sources. Double-glazed windows provide excellent long wave radiation blockage and they also store energy in the form heat between the two layers of glass.
- Storage – some of the collected solar energy is immediately used in the living spaces and the rest is stored for later use. Thermal mass is usually the concrete, stone, brick and also water which could absorb and store heat from the incident solar radiation and release it slowly as and when the temperature in the inner building space falls.
- Distribution – heat stored in the thermal mass is slowly released by conduction (within the surface heat transfer), convection (through air flow) and radiation. In a hybrid passive solar system; fans, vents and blowers could be used to distribute heat.
Sun-spaces – The most attractive passive solar setup is the attached sunspace also known as solar green house or conservatory. An attached sun-space to the parent house acts as a solar collector which also serves other building functions. It pre-warms ventilation air for the house and offers the benefit of lower energy bills and also is the most comfortable area of the house on a sunny winter day. They collect solar energy during the day to transfer it to the rest of the house and during nights and cold days it acts as a buffer, reducing heat loss. Sun-spaces are also operated as hybrid systems in which a fan is used to transfer heated air from the sun-space to other building spaces or to storage.
A good passive solar design must have answered the following questions to experience maximum benefits:
- How long is the solar radiation available and at what intensity at different times of a year in the selected site?
- How much sun’s heat does the building require for the occupants to be comfortable?
- How much storage capacity should be in place to provide for the heating requirements?
- Is there a necessity for additional systems or equipment for controlling heat gains from solar radiation and how they can be implemented with suitable envelope performance, building form and ventilation?
Passive solar heating systems are said to provide 30 – 70% of residential (single family) heating requirements depending on the size of the system and whether it is a natural system or a forced hybrid system. Other factor which influence the energy savings are the level of energy conservation being employed in the building fabric and the local climate. Economic analysis of passive solar systems including capital costs suggest they offer a good payback. Exclusive capital cost can usually be avoided if the building owner adopts a passive solar design for his dwelling like including a conservatory or windows and glass facades on the south facing wall for maximum utilization of solar radiation. The effectiveness of the technique varies however from site to site. Professional advice and design guidance for an energy efficient building is a potential investment for future energy and cost benefits.
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Show/Hide Comments (3)
By Nissan Xterra Supercharger on 08/27/2010
It pre-warms ventilation air for the house and offers the benefit of lower energy bills and also is the most comfortable area of the house on a sunny winter day. They collect solar energy during the day to transfer it to the rest of the house and during nights and cold days it acts as a buffer, reducing heat loss….
By Green Home Windows on 10/21/2010
I have always said that there is always a more efficient way of doing things. Building a home with passive solar technology can save you so much more in the long run, and result in a cleaner environment.
By John S. Heat on 12/25/2011
Wow this is an informative article on how to make proper use of solar energy. I am thinking of using solar energy to run my heating at night, and this just gave me some inspiration to work on!
